The human skin is variously colored, showing individual variations even within racial groups. The appearance of the skin is mainly determined by melanin, a pigment manufactured by melanocytes which are found among the basal cells of the epidermis.
Melanin is a water-insoluble polymer of various compounds derived from the amino acid tyrosine. It is one of two pigments found in human skin and hair and adds brown to skin color; the other pigment is carotene which contributes yellow coloring. The synthesis of melanin reactions is catalyzed by the enzyme tyrosinase. Tyrosinase is found in only one specialized type of cell, the melanocyte, and in this cell melanin is found in membrane-bound bodies called melanosomes. The various hues and degrees of pigmentation found in the skin of human beings are directly related to the number, size, and distribution of melanosomes within the melanocytes and other cells. Besides its role in pigmentation, melanin, which absorbs ultraviolet light, plays a protective role when skin is exposed to the damaging rays of the sun. It is melanin, produced in response to the stimulus of UV light, which is responsible for the tanning of the skin.
Although the heterogeneous distribution of melanin in the skin, for example, in the form of freckles or moles, is considered by some as a defining characteristic of beautiful skin, such “beauty marks”, on the other hand, often are found to be less desirable by others who seek to lighten these darkened areas of the skin. Even in cases where the skin is homogeneously dark, it is often desired to lighten the skin overall.
Various classes of whitening agents with different skin lightening mechanisms and effects are known. For example, tyrosinase inhibitors, such as kojic acid, interfere with the synthesis of melanin in the melanocytes of the skin, therefore reducing the total amount of melanin in the skin. Certain bleaching agents, such as hydrogen peroxide, hydroquinone, 4-isopropylcatechol and hydroquinone monobenzyl ether, lighten the skin by decomposing or reducing already formed melanin in the skin. Certain exfoliants, such as scorbic acid, salicylic acid and lactic acid, have also been used as whitening agents, and they achieve the skin lightening effects by causing the top layer of the skin to shed. Further, yeast extract or live yeast belonging to the genus Saccharomyces has been known to exhibit a melanin-decomposing or melanin-suppressing effect and therefore has been used in whitening compositions.
Resveratrol, also referred to as 3,5,4′-trihydroxystilbene, is a polyhydroxy-substituted compound found in red grapes, raspberries, blueberries, and certain other plant berries or extracts. There has been reports that resveratrol exhibits various anti-cancer, antiviral, anti-aging, skin whitening, and antioxidant effects, and it has been incorporated into a variety of cosmetic formulations, such as skin creams. However, one problem with resveratrol is that it is generally unstable in cosmetic formulations. Accordingly, if used in cosmetic formulas, it can only be used in very small amounts. If present in too large an amount, the resveratrol will hydrolyze and cause the cosmetic formulation into which it is incorporated to become discolored.
Ferulic acid has long been recognized for its skin whitening and antioxidant effects on skin. However, ferulic acid readily undergoes undesirable decomposition at a relatively low temperature and lacks long-term stability. Therefore, formulation of ferulic acid into cosmetic compositions has proven to be generally difficult, due to issues related to product stability and shelf life.
It is an object of the invention to provide new chemical compounds with not only enhanced skin lightening, anti-aging, and antioxidant effects, but also significantly increased color stability and extended shelf life, which can be readily formulated into various cosmetic or pharmaceutical compositions for topical, oral, transdermal, intravenous, intramuscular, intraperitoneal, intrasternal, subcutaneous, intraarticular, intranasal, sublingual, pulmonary, or rectal administration.
It is a further object of the invention to provide aesthically pleasing and stable cosmetic compositions that are commercially acceptable.